Off The BallIreland's most popular sports show and winner of a record nine PPI radio awards hosted by Ger Gilroy, Kevin Kilbane and Joe Molloy. Monday to Thursday from 7pm - 10pm, Fridays from 7pm - 9pm, Saturdays from 1pm - 6pm and Sundays from 12pm - 6pm.

It was a mysterious crime which baffled the FBI: a skyjacking which saw a businessman jump out of a plane with ransom money, never to be seen again.

But nearly 45 years on from the daring heist, investigators are closing the unsolved case for good after failing to identify the criminal who became known as "DB Cooper".

On the night before Thanksgiving in 1971, the hijacker in a business suit told an air hostess on a flight from Portland to Seattle that he was carrying a bomb - and demanded US$200,000 in cash and four parachutes.

The plane touched down in Seattle to collect the ransom money, and although all 36 passengers were released, the man ordered the plane's crew to fly towards Mexico.

Under his instruction, the Boeing 727 flew slowly at a height of just 10,000ft - and over Washington state, the hijacker lowered the plane's rear stairs and jumped into the freezing rain.

Cooper asked for four chutes in all - he jumped with two (including one that was used for instruction and had been sewn shut). He used the cord from one of the remaining parachutes to tie the stolen money bag shut.

Nine years later, a boy digging on a beach discovered three bundles of damaged $20 bills worth US$6,000 which matched the serial numbers of the cash given to Cooper.

Left: During the hijacking, Cooper was wearing this black J.C. Penney tie, which he removed before jumping; it later provided a DNA sample | Right: Some of the stolen $20 bills found by a young boy in 1980 | Image: FBI

But despite an investigation which became one of the longest and the most exhaustive in the FBI's history, the trail went cold - and the bureau says it's time to focus on other cases.

"Although the FBI appreciated the immense number of tips provided by members of the public, none to date have resulted in a definitive identification of the attacker," officials said in a statement.

"It's a mystery, frankly. We've run down thousands of leads and considered all sorts of scenarios. And amateur sleuths have put forward plenty of their own theories. Yet the case remains unsolved," the statment adds.

One of the parachutes left behind by Cooper and the canvas bag it came in | Image: FBI

Evidence from the case is going to be preserved at the FBI's headquarters, but detectives will only examine further tips if Cooper's parachutes or ransom money are discovered.

There have been countless conspiracy theories about the identity of the hijacker and whether he survived the plunge.

Reports of unexplained wealth have been examined by detectives, with one woman telling the FBI that her late uncle had turned up to Thanksgiving dinner in Oregon - where the ill-fated plane had taken off the day before - with serious injuries.

Off The Ball

Ireland's most popular sports show and winner of a record nine PPI radio awards hosted by Ger Gilroy, Kevin Kilbane and Joe Molloy. Monday to Thursday from 7pm - 10pm, Fridays from 7pm - 9pm, Saturdays from 1pm - 6pm and Sundays from 12pm - 6pm.